BACILLUS-COLI-LlKE BACTERIA FROM FECES AND SEWAGE 31 



Salicin is fermented, with gas-formation, by 102 organisms after 

 72 hours at 37 C, while 54 strains do not form gas. Among the non- 

 gas-formers, 10 (18.5%) produce 0.4-0.8% normal acid, whereas 

 this quantity of acid is also formed by 20 (19.6%) of the gas-formers. 



It appears from Table 12 that under the conditions of these experi- 

 ments, acid-production in sucrose, dulcitol, and raffinose is well corre- 

 lated with the presence or absence of gas. With salicin the correlation 

 is not so marked, while with glycerol the line of demarcation between 

 gas-formers and nongas-formers, as indicated by the quantity of acid 

 produced, is very indistinct. The substitution of quantitative acid- 

 production for gas-formation would therefore be particularly undesir- 

 able when working with glycerol. 



These results are well in accord with those of Winslow and 

 Walker, 8 who observe: "Gas-formation coincided with acidity except 

 in the case of dextrin." Unfortunately, acid-formation in dextrin was 

 not determined in this study, and Winslow and Walker did not employ 

 salicin or glycerol. 



CHARACTERISTICS OF ORGANISMS FROM THE DIFFERENT SOURCES 



When this study was begun (1915), motility and fermentation of 

 dextrin and starch were regarded as of little significance and hence 

 these tests were omitted. In the following year (1916) the possible 

 significance of the reactions was realized and, as the cultures were 

 still available, they were tested out. Motility was determined in a 

 soft agar medium consisting of nutrient broth and 0.5% agar. 



In Table 13 are shown the number and percentage of organisms 

 giving positive reactions with the various tests. Glucose, galactose, 

 mannitol, maltose, and lactose are fermented by all strains, with gas- 

 production. Inulin is not fermented by any of the organisms, and 

 gelatin is uniformly negative in 20 days at 20 C. Gas is formed from 

 glycerol by 76.2%, from salicin by 66.1%, from raffinose by 50.7%, 

 from sucrose by 48.7%, from dulcitol by 43.6%, from dextrin by 5.1%, 

 and from starch by 4.5%. The Voges-Proskauer reaction is given by 

 5.8%, indol is produced by 91.1%, and 61.5% are motile. 



Table 14 shows the characters of organisms isolated from different 

 sources. Characters which are negative or positive for all strains are 

 omitted. 



Several things are evident. Organisms giving a positive Voges- 

 Proskauer reaction or gas from dextrin and starch were obtained 



